1. Field of the Invention
This invention relates to a method of producing a composite ceramic body. More particularly, it relates to a method of producing a ceramic material having a surface covered with an amorphous ceramic film which gives it a high degree of strength, especially when it is brought into point contact or Hertz's contact pressure with another object.
2. Description of the Prior Art
Ceramics, such as silicon nitride (Si.sub.3 N.sub.4) and silicon carbide (SiC), are expected to be very useful as materials for constructing various kinds of structures. They are very hard and excellent in heat resistance. They, however, also have the drawback of being brittle. It is necessary to eliminate this drawback in order to render them useful for a wider scope of application. The attempts hitherto made in this connection have mainly been to improve the materials per se. They have, for example, included the partial stabilization of zirconia (ZrO.sub.2) and the addition of ZrO.sub.2 to alumina (Al.sub.2 O.sub.3). All of these attempts have been intended for preventing the fracture of the material by the stress-induced phase transformation of ZrO.sub.2. None of these methods is, however, applicable to all kinds of ceramics.
An another attempt has recently come to be made to improve the drawback of a ceramic material by irradiating ions on its surface. For example, it is known that the irradiation of ions on the surface of Al.sub.2 O.sub.3 for making it amorphous makes it easily deformable and thereby restricts its fracture. This method is, however, effective only under limited conditions. For example, the formation of an amorphous surface on Al.sub.2 O.sub.3 requires cooling by liquid nitrogen during ion irradiation, though it permits the use of nitrogen ions which are relatively easily available.
And this method is not applicable to all kinds of ceramics, an amorphous layer cannot be formed on some ceramics.